Physical modeling of salt leaching on samples of ore material without construction of three-dimensional models of underground chambers significantly simplifies research and yields more reliable data.Valid modelling of the process of brine formation in an underground leaching chamber, which is most important and interesting from the practical point of view, requires simultaneous modelling of the processes of hydrodynamics and mass exchange occurring therein [1][2][3][4].To establish the modelling requirements for an underground leaching chamber, let us consider the entire complex of these processes, which, according to the well-knownwork of Kulle [i], can be described by systems of differential equations, which specify the conditions of motion of a viscous incompressible liquid (the Navier--Stokes equation), the convective diffusion of matter, the conditions of spreading of matter at the interface between the boundary layer and the main bulk of the solvent, and the conditions of mass exchange at the phase interface.Scale transformation of these equations gave the following system of similarity criteria:Hydrodynamic similarity criteria:Re: Wl/v;, Fr-= W~/gl; Eu:gAP/pW 2" (l)Criteria for a steady process:Diffusion mass exchange:Concentration criterion:Here W is the linear velocity in m/sec, p is the density in kg/m S, Z is the linear dimension in meters, ~ is the coefficient of kinematic viscosity in m2/sec, D is the diffusion coefficient in me/see, r is the time in seconds, k is the solution rate constant in m/sec, and C i and Cf are the saturation concentration and the final concentration of the brine in kg/m s.The slowest phase, which determines the rate of the overall process of brine formation in the leaching chamber, is mass exchange in the boundary layer [i, 4]. It has been suggested [5] that the boundary layer should be divided into a low-mobility diffusion or Prandtl layer immediately adjoining the salt surface, with the main diffusion resistance, in which mass exchange is due mainly to molecular diffusion, and a more mobile, so-called hydrodynamic layer, in which mass transport predominates over convective diffusion.